Deflecting coil



Jan. 9, 1940. E. RUSKA 2,186,595

FLECTIN Jan. 9, 1940. E, RUSKA 2,186,595

DEFLECTING COIL Filed Aug. 5, 1936 2 Sheets-Sheet 2 INVENTOR,

BY v M ATTORNE Patented Jan. 9, 1940 PATENT OFFICE DEFIQECTING con.

Ernst 'Ruska, Berlin-Zehlendorf, Germany, as-

signor to the firm Fernseh Aktiengesellschaft, Zehlendorf, near Berlin, Germany Application August 5, 1936, Serial No. 94,434 In Germany October 24, 1935 The present invention relates to particular forms of deflecting coils for use in Braun tubes, and is a further development of the coils disclosed my UnitedStates application, Serial No. 80,886, filed May 20, 1936, entitled Magnetic deflecting system for Braun tubes.

In that disclosure it was explained that a more truly linear response was, obtained to a linear beam deflecting current if the deflecting coils were oftrapezoidal outline, with the parallel bases disposednormal to the undeflected ray axis of the Braun tube, the shorter of the bases being dis- ;posed nearer the electron gun and the longer coil systems, each formed of two trapezoidal coils,

are assembled for deflecting the ray in two directions,"they define a central open portion inthe form of a truncated pyramid symmetrically dis- N posedabout the undeflected ray axis of the tube,

'20 with its smaller end turned toward the beam source and its larger end directed toward the screen.

In my United States application referred to above, a truncated pyramidal coil form was shown 25 having a longitudinally (parallel to the ray axis) corrugated surface, the corrugations diverging evenly from the small toward the large end, so that coils might be wound about the form, with the corrugations serving as guides. It has some- 30 times been found diflicult however, when using such a coil form of proper size for a particular cathode ray tube, to wind thereon a suflicient length of wire to produce the required ampereturns, considering all other necessary factors.

35 To retain the advantages of the trapezoidal coil form, the present invention discloses the use of a coil wound in a flat plane about a trapezoidal form, the coil being then bent to a desired shape.

Other objects of my invention will be apparent 40 or will be specifically pointed out in the description forming apart of this specification, but I do not limit myself to the embodiment of the invention herein described, as various forms may be adopted within the scope of the claims.

45 In the drawings, Fig. 1 shows a fiat trapezoidal coil.

Fig. 2 shows the coil of Fig. l with the parallel end conductors (those forming the bases of the trapezoid) bent around.

50 Fig. 3 shows a flat coil wound on a modified trapezoidal plan, the longer base being curved convexly, and the side conductors being disposed divergently toward the convex base.

Fig. 4 shows two coils, such as shown in Fig. 3,

55 with their parallel base portions so bent around showing the manner in which the deflecting coils being disposed further away. When two such 14 Claims. (01. 250-157) that the side conductors of each coil lie adjacent those of the other in a flat plane.

Fig. 5 is a side elevation of a cathode ray tube are applied thereto.

Fig. 6 is a partially sectional schematic view of the tube and coils taken on line 65 of Fig. 5.

Fig. 7 is an elevational view of the complete coil assembly showing a preferred form of mounting. 19

Fig. 8 is a partially sectional view of the coil structure.

In Figs. 1 and 2, I designates the conductors forming the shorter base of the trapezoid, 2 designates those forming the longer base, parallel to those of conductors I, while 3 and 4 designate the side conductors. When the end conductors l and 2 are bent around as shown in Fig. 2, side conductors 3 and 4 will lie, when placed inposition in the cathode ray tube, not shown, parallel to the ray axis, and divergent away from the electron source in one plane. In the direction of the beam deflection, however, the conductors 3 and 4 are non-divergent, and the field therefore does not produce, at the outer limits of the beam deflection, a linear response.

If, however, the side conductors are wound with a divergence therein toward the longer base of the trapezoid, as shown in Fig. 3, this condition can be remedied.

The side conductors 3 and 4 in Fig. 3 may be wound divergently by inserting wedge shaped insulating strips ID, shown in Fig. 8, between adjacent side conductors 3, or in any manner well known in the art. The conductors 2 of the longer base of the trapezoid in Fig. 3 must be bent convexly away from the shorter base I in order that, when the end conductors I and 2 are bent, as in Fig. 4, the side conductors 3 and 4 of opposite coils may abut in a line parallel to the undeflected ray axis, and yet the end conductors l and 2 may lie in a plane perpendicular to that axis. Adjacent side conductors 3 and 4 lie in a flat plane: the opposite fiat planes formed by each adjacent pair of side conductors 3 and 4 are divergent in the direction of the undeflected ray axis, and the individual component side conductors of groups 3 and 4 are so spaced, by reason of their divergent winding, that the conductors opposite the ray, at any degree of deflection thereof, will be parallel thereto, whereby a uniform deflecting field is obtained, and a linear deflection of the ray is produced in response to a linear deflecting current, regardless of the angle of deflection.

In Fig. 5, I have shown the manner in which the coils, properly bent, are disposed about the neck of the cathode ray tube H. The opposed coils l2 and M are positioned with the side conductors 3 and 4 lying in a flat plane, adjacent edges being parallel to the undeflecting ray axis of the tube. In Fig. 6, I have shown the coils as they appear from the cathode end of the cathode ray tube when placed in position about the neck of the tube H. The coils l2 and I4 provide for uni-lateral deflection of the cathode ray beam.

To complete the beam control, it is necessary to i 1 provide a second pair of coils positioned to set up a deflecting field at right angles to that of the first pair of coils. Such a second pair of coils, l5 and I6, may be proportioned to extend over and about coils I2 and It, as shown in Fig. 7, and they may be held in place by any convenient supporting means, such as an insulating box 11. Any other suitable supporting means is deemed a full equivalent, however, of the embodiment shown.

The coils may be formed mechanically in any way known in the art, using pulverulent insulating material for the supports which is permanently shaped by applying heat and pressure, if desired. Any suitable supporting means is deemed fully covered in my disclosure.

I claim; I

1. In combination with a cathode ray tube having an electron gun therein, deflecting coils of modified trapezoidal form, having a short base portion adapted to be disposed perpendicular to the axis of said tube near said electron gun, a longer base portion disposed perpendicular to said tube axis away from said gun, and side portions connecting said end portions, said side portions having conductors disposed in fiat planes divergent away from said gun and about said tube axis, said conductors being divergent within said fiat planes.

2. A coil for use in a cathode ray tube, said coil being formed in a fiat plane and of modified trapezoidal form, having a straight short'base portion, a longer base portion bent convexly away from said straight base portion, and side portions connecting said end portions, said side portions having therein conductors spaced divergently from each" other toward said bent base portion, said flat coil being adapted to have said end portions bent.

3. A deflecting coil portion bent convexly away from said short portion, and side portions connecting said end porsaid ray, said small end portion being. closer to said gun than said larger end portion,'. andbside conductor portions connecting said end portions,

said side conductors being so positioned and arranged as to lie in flat planes with said side con-- ductorsof each coil being in the same plane with adjacent side conductors of the other coil, said planes being divergent in the direction of the undeflected ray axis of said tube away from said gun, said side conductors lying in saidflat planes being divergent in the direction of the axis of said tube away from said gun.

ERNST RUSKA.

. 1Q for use with a cathode ray tube, having a modified trapezoidal form comprising a straight short base portion, a long base wmwm l5 tions having conductors divergently spaced away 

